IIRC, 3.2mA is somewhat high for a pi's GPIO to provide - for single LEDs a series resistor of ~220 - 560 ohms (depending on LED colour) is more common (associated with a current of ~1mA). Hence my use of 3.3V to 5.0V level shifters and 5V I.C.'s capable of providing greater (or controlled, limited) currents. FWIW, there are other example LED display circuits within my webpages (as well as the "early" one I linked to).MarkDH102 wrote: Thanks for all your suggestions.
The displays are red.
I drove individual segments on a breadboard to start with for testing purposes using the 3.3v supply from an Arduino Uno via a 22 ohm resistor and measured 3.2mA per segment.
I use the code on other projects so I will set to checking my wiring...
It is a chip or package limitation. The 50mA-per-bank limit is included in the Compute Module datasheet, where you provide your own power supplies.drgeoff wrote: ↑Wed Nov 22, 2017 10:04 pmThere is also a supposed maximum of a total of 50 (fifty) mA for all GPIOs but I don't recall seeing an authoritative answer of whether this is a chip limitation which still applies or was all that was available from the linear 3.3 volt regulator on earlier model RPis once the on-board stuff took what they need.
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